In this illustration, we see two laptop computers positioned side-by-side; the computer on the left is labeled "Source" and the computer on the right is labeled "Destination." Each computer has a dotted arrow extending vertically downwards, representing the passage of time. A very small portion of the timeline directly below the source is designated as "DIFS." Below this portion is a wide dark blue band, labeled "data" that extends diagonally downward to the right from the source timeline to the destination timeline. There is a small gap in the destination timeline, labeled "SIFS," followed by a thinner light blue band, labeled "ack," that extends diagonally downward to the left from the destination timeline to the source timeline.